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Evolution of Darwin's Evolution Theory:
I turned CNN on just as an everyday routine, before I moved on to other channels, with the hope that I would update myself with today's news quickly and then move on to something else. Suddenly I heard that the Georgia School Board had initially decided to take the word "evolution" out of the textbooks and replace this controversial word with the words "biological changes." But at the end of the report, the person who was in charge of making this change had to back up because of strong protest from the scientific community. She apologized and said she was sorry that she started a bigger controversy, when her intentions were to move away from the initial controversy about evolution. I almost stopped breathing when I started to listen to the news, and then I sighed when heard the end of it. I was drowning in the waves of my thoughts, worrying about my seven-year old daughter, who is already asking questions about creationism and religion versus atheism/freethinking/women's right etc. what would she learn from these schools if this was how science was perceived here? This is not the first time this has happened in the USA and the Western world, places the rest of the world looks up to for scientific developments. Dr. Tim M. Berra, Professor of Zoology at the Ohio State University, wrote a book called Evolution and the Myth of Creationism: A Basic Guide to the Facts in the Evolution Debate The book's purpose was to refute and protest the surge of non-scientific material in the United States school board curricula. He stated his anger and frustration in the preface of the book ... "I was originally drawn into the evolution/creation controversy in 1982, when I reviewed a draft of the Biology Curriculum Guide of the Columbus, Ohio public schools. Until then, I had shared the view of most scientists that the creationists were not to be taken seriously. Just ignore them, and their demands will soon be forgotten ... was the attitude of busy scientists who did not want to interrupt their research to do battle with quaint notion of bygone age . . . I was shocked to see that the Biology Curriculum Guide, a handbook for high school biology teachers, was about fifty percent creationist. It considered such fundamentalist Christian beliefs as that the Earth is only few thousand years old to be a scientific equal of modern radiometric-dating techniques. Along the way it trotted out the usual creationist chestnuts--misrepresentation of the Second Law of Thermodynamics, distortion of fossil records, the claim of worldwide flooding, and many examples of anti-science--passing them all off as science. That was when I realized that education is in trouble! It was clear that the strategy of ignoring the creationists would work to the detriment of both science and society." I had heated discussions with many of my friends from the scientific and progressive communities, who had so many misconceptions about evolution, Darwinism, and scientific advancements in these fields. They tried to portray the limitations of Darwin's theory and the new findings in this area as a strong support for creationism. Because Einstein was wrong about the Uncertainty Principal of Heisenberg, however, that did not prove that the whole discipline of quantum physics was wrong. Because Darwin had limitations in his theory of evolution, which he proposed almost 140 years ago, it does not prove that the scientific approach to the evolution of all living creatures in this world has been proven wrong, and that creationism has won. Religion is based on sheer belief; it does not have any scientific basis. Religious people's interpretations are not subject to experimentation, revision or falsification. According to religion, the only way one can know the truth is for God to tell him/her what it is. Whatever contradicts the holy scriptures has to be wrong, in their view. The theory of evolution, on the other hand, is based on a scientific approach. It has been going through experimentation, modifications, and expansions every day with the speed of light, as science progresses.. Science does not rest on beliefs; it is a self-correcting endeavor. Science depends on hypotheses, tests, logic, proofs, and the rationality of a proposed hypothesis or theory. If evolution gets proven wrong by critical new data, scientists would be the first ones to discard it and move on to the new research for the sake of their own careers. The scientific community has undoubtedly accepted the theory of the evolution of life. This is the foundation of the biological sciences. Think about it for a moment; Darwin did not have abundant information on geological longevities of fossil records, and had no idea about genetics when he proposed this evolutionary theory. The more advancement have been made in the area of Geology, radioactive dating technology, paleontology (scientific study of fossils), microbiology, and genetics, the more concrete are the records that have been piled up that support of theory of evolution. Darwin was far ahead of his time. But there are many disagreements and hypotheses about how this evolution takes place. Today one of the most debated topics is Darwin's natural selection, which upholds the gradual evolution of species. Scientists differ greatly about this notion. While debates and experiments heat up among the scientific community around the tempo of evolutionary change, one thing has been proven to be certain: Darwin was absolutely right about evolution. Before I get into a more detailed discussion on Darwin's theory of evolution and how it has evolved in almost one and a half centuries, and how his book On the Origin of Species by Natural Selection first shook the world in 1859, let me explain some of the scientific terminologies that I will use throughout the discussion. Darwin noted that every individual within a species was unique (Species are basic units of life; a species is a group of animals or plants that is capable of breeding successfully with each other), and that no two individuals were exactly alike, except for rare examples of identical twins in nature. He explains that there is immense variation in Nature; its reproductive capacity is far greater than the real population size. Darwin concludes that there is competition in nature for resources that overproduction of offspring is the rule for nature, and that only favorable variations get to survive and flourish and the unfavorable ones die out. Darwin called this process natural selection, and stated that, as a result of natural selection, biological evolution occurred. (Interestingly enough, Darwin never mentioned two things in his writings that he gets so much credit for from supporters and critics alike: one is the word"evolution," and the other is the phrase"survival of the fittest". According to Darwin this natural selection is a very slow and gradual process and gets reflected in adaptation. Organisms get adapted and fine tuned for survival through their environments.. As I have mentioned before, Darwin proposed his theory of evolution without the help of genetics, and with limited knowledge of fossil records. As these two disciplines started to grow in the beginning of 1900s, Darwin's theory of evolution got reaffirmed on the basis of strong scientific data. Gregor Mendel's discovery of genes (units of heredity within a cell) resolved many of the problems Darwin was having with inheritance. Mendel's study showed that all traits are inherited by the random combination of genes coming from each parent though they never get blended, but that their effects are sometimes diluted by other genetic traits. Some genetic variants adapt better to their existing natural environment and survive until maturity, leaving enough offspring to carry their genes. On the other hand, the less well-adapted variants die out, leave fewer offspring, and gradually disappear from nature. As a result, the frequency of the occurrence of certain genes changes over time. In summary, evolution is a change of gene frequency brought about by natural selection and other processes acting upon the variations produced by sexual reproduction, mutation and other mechanisms. The environment is the selecting agent, and because the environment changes over time and from one region to another, different variants will be selected under different environmental conditions. To understand it better, let's consider this example from our everyday life.. Why do doctors always insist on completing the dose of an antibiotic when you get sick? After a few days of the drug you do feel better, because the antibiotic has killed most of the susceptible bacteria. But you still have only those bacteria left in your system which are more resistant to the drug. If you quit taking the antibiotic at this point, only these more resistant bacteria will produce their next generation of offspring with a much more resistant gene pool. In a few days you could feel much sicker, and be infected with a much more resistant group of bacteria. You would need a much stronger medicine to destroy them. What happened there would be that more drug resistant bacteria were selected for survival. Antibiotics did not make the bacteria more resistant; they just created an environment which encouraged the micro-evolutionary shift towards a new strain. Darwin only focused on adaptive causes and natural selection. Though he suspected the existence of other non-adaptive changes, he did not have the opportunity to appreciate it in the light of modern genetics. Gradual natural selection is the primary force causing evolutionary changes, but it is not the only force. As modern genetics came into play in between the 1900s and the1920s, scientists started to discover that chance fluctuation in gene frequencies could yield some net changes. Genes are chemical structures, and sudden, accidental heritable modification through chemical changes in gene is called mutation. Mutation can occur more than once, and it can disrupt or change the character of a population even before it has gone through the process of natural selection. Very prominent biologists like William Bateson, Hugo de Vries, and T.H Morgan argued that unusual mutants explained the immediate mode of change in nature, and that this was more tangible and self explanatory than the Darwinian selection mechanism. They concluded that the accumulation of many mutations resulted in the biological evolution of life. It became widely accepted that new species evolved from macromutations, not from a gradual process of natural selection leading to evolution. Darwinism appeared to be dead. In the meantime, advancement in the modern synthesis of evolution and population genetics started to get serious attention in the field of modern genetics. Changes in gene frequency could be calculated mathematically. Now we know genes are arranged in a linear fashion on chromosomes composed of DNA, and of protein which resides in the nuclei of animal or plant cells. Sudden or accidental macromutation cannot create a species instantly; it can only create random variability in small degrees. Only occasional and small mutations can be valuable to nature and improve adaptation. The theory of macromutation as the primary force of evolution got discarded, though it found an important place in new evolutionary genetics. Modern synthesis reaffirmed Darwin's gradualistic evolution theory. Dr. Dobzhansky was the pioneer of this new re-affirmation of gradual evolution. His intense experiment with fruit flies (Drosophila) showed that seasonal genetic alterations occur due to the changing environment, proving natural selection. He wrote in 1947, "Controlled experiments can now take the place of speculation ... The mechanics of natural selection in concrete cases can be studied. Hence the genesis of adaptation, which is possibly the central problem of biology, now lies within the reach of the experimental method." Through modern synthesis and the development of quantitative population genetics, evolutionary biology entered a new era. It was elevated from speculation to experimental science embedded in to mathematical calculation, just like physics and chemistry. Darwin's gradual and slow selection process works perfectly on large populations, as the accidental genetic changes even out at the end. But in the case of small populations, genetic drift (random changes in gene frequency by accidental or chance occurrences) plays the most important role. Natural selection does not work in cases of small populations as it does in large populations. A similar phenomenon can be observed in case of the founder principle as well. For example, a self-fertilizing black snail gets blown out to a small island where no other snail is available, and it produces lots of black snails by self fertilization. Now the new colony of snails will have a very different gene frequency as the parent snail brought an incomplete sample of genes from the original gene pool. This change will occur due to chance, not because of natural selection. These are all examples of non-adaptive selection that Darwin did not cover in his findings. Discovery of the most famous transitional fossil, Archaeopteryx, has been a major triumph for the supporters of gradualist evolution theory. T.H. Huxley showed very clearly that this was an intermediate between small dinosaurs and birds. It had the skeleton of a dinosaur and the feathers of a bird. It might not be the ancestor of modern birds, but it shows the clear transition from reptile to birds. As radiometric dating technique developed later, we started to get more and more evidence supporting evolution. We can now determine the absolute age of ancient rocks and the fossils embedded in them. . The oldest fossils of bacteria and algae date back 3.5 billion years. We find better and more developed forms of life as the layers of rocks get younger and younger. This sequential appearance of more advanced life forms in different layers of rocks only confirms Darwin's theory of evolution.. On the other hand, fossil records also contradict Darwin's gradual and stepwise changes as the principle mechanism of evolution. Fossil records clearly show that there are lengthy periods of very little change, and then suddenly we see very rapid changes again followed by very slow changes. This has been a major area of research in the field of recent evolutionary biology. Many new theories have emerged to explain this gap. First Ernest Mayr and then paleontologists Niles Eldredge and Stephen J. Gould have suggested that some species have evolved rapidly, going through a sudden burst of relatively rapid evolution diverging quickly from its ancestral species. This theory has been known as punctuated equilibrium, and seems to contradict with Darwin's gradual evolution. The supporters of this theory point towards the fossil records where we can find abrupt appearances of new species or abrupt disappearances of existing species. Richard Dawkins has opposed this theory by pointing out that it could have resulted from migration into an area. Dr. T. Berra states,"Punctuated equilibrium is really just accelerated gradualism. The punctuated equilibrium proponents compress gradual changes into brief episodes. Gradual change means that the descendants are only slightly different from their ancestors. Even though there might be geological brief bursts of evolution followed by long periods of no change, the change that occurs is still gradual, or stepwise." Dr. S.M. Stanley says,"Some workers assumed that the punctuational view virtually denied evolution within established species; conversely, they assumed that the gradualistic view saw speciation as almost never being rapidly divergent. Because it then seemed evident that the truth lay on the middle ground, the controversy seemed meaningless and misleading ... As I have noted the biggest problem, the sudden rise of flowering plants--Darwin's 'abominable mystery'-- has been resolved by new fossil evidence. We now have fossils documenting a pattern of early adaptive radiation. Here we have a prime example of how the concept of evolution has been strengthened rather than weakened since the time of evolution." So we see that, though this very contradictory evolution theory has gone through brutal refutation and challenges, it has gotten stronger every day because of new developments in science. All these new theories have only strengthened the concept of evolution. The theory of evolution has stood the test of time, though the mechanisms and tempo of evolution have constantly been debated. We have seen immense hatred and fear towards this theory from the creationists. Maybe history is repeating itself--when Copernicus proposed that the earth was not the center of the universe, the Roman Catholic church considered it to be blasphemy. It took hundreds of years before everybody agreed to accept this simple scientific fact that the earth was moving around the sun with all other planets. This time Darwin has displaced the human species from center stage, where human beings have thought themselves to be the best creatures, created by a divine force. It will very understandably take a while before we can swallow this immense shock and embrace the scientific fact of evolution. e-mail: bonna_ga@yahoo.com
References: The New evolutionary Timetable: by Steven M. Stanely: Dept of Peleobiology at John Hopkins University The Structure of Evolutionary Theory: by Stephen Jay Gould: Dept of Zoology at Harvard University The Selfish Gene and The Blind Watchmaker: by Richard Dawkins at Oxford University. Evolution and the Myth of Creationism: by Tim M. Berra at Dept of Zoology at The Ohio State University The great Evolution Mystry: by Gordon R. Taylor, chief Science Advisor at BBC. Genetics and the origin of Species: T. Dobzhansky at Columbia University. |
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